1. Field of the Invention
The present invention relates to a method for displaying a document image with a large number of pixels and at high resolution, which is captured from an image input device such as a scanner, etc., and more particularly to a method for displaying on a display screen whose number of pixels is smaller than that of an image to be displayed.
2. Description of the Related Art
In recent years, portable information devices such as a PDA (Personal Digital Assistant) have become popular. These portable information devices are compact in size and easy to carry, but their capabilities must be incorporated into small-sized bodies. That is, there are restrictions that their CPU performances and storage capacities are smaller and their display screens are of as small as some inches and the number of pixels to be displayed is small in comparison with generally used desktop PCs. For example, the number of pixels to be displayed by a desktop PC (the resolution of a desktop PC) is 1,024xc3x97768 pixels to 1,600xc3x971,200 pixels, while the number of pixels to be displayed by a portable information device (the resolution of a portable information device) is approximately 320xc3x97240 to 640xc3x97480 pixels.
Meanwhile, a digital still camera of a small size with high performance, and a handy image scanner of a small size has become popular as image input devices. There is the demand for capturing an image in conjunction with a portable information device regardless of time and place. The number of pixels of a photo taken by a digital still camera is approximately 320xc3x97240 pixels to 640xc3x97480, and is suitable for capturing a natural image and a solid body such as a landscape, a man, etc. as a color image. Since an image scanner can scan an image at high resolution of 200 to 400 dpi (dots per inch: the number of pixels within the space of one inch), it is fit for capturing a document image. However, the number of pixels and the amount of data are large in contrast to the high resolution. For example, the number of pixels of an A4-sized document image captured at a 400 dpi is 3,400xc3x974,600 pixels, and its data size is approximately 2 MB even if it is binarized.
When a document image is captured by connecting a handy scanner to a portable information device, there is the demand for reusing document image data such as transferring the image stored in the portable information device to a desktop PC and electronically filing the image, or performing character recognition (OCR: Optical Character Recognition) and converting the image into text data, etc. To satisfy this demand, the document image must be scanned and captured at high resolution.
However, because the number of pixels of a scanned document image is larger than that of a display screen of a portable information device, the entire document image cannot be displayed as it is. Assume that the display screen of the portable information device is at a resolution of 640xc3x97480 pixels, and the scanned image is at the above described resolution of 3,400xc3x974,600 pixels (A4 size), the difference of the number of pixels between these two is 60 times. Accordingly, the document image must be converted by some means or other in order to be visible on a display screen.
With a conventional method for displaying a document image, if a document image whose number of pixels is large, and which is captured from an image input device such as a scanner, etc., is displayed on a display screen whose number of pixels that can be displayed is smaller than the number of pixels of the captured document image, the document image is reduced and displayed by adjusting the image to the width and height of a display area in order to match the number of pixels of the display area on the display screen, so that the entire image is displayed (Japanese Laid-open Patent Publication (TOKKAISHO) No. 62-186370). Assuming that the document image shown in FIG. 1 is displayed on the display screen, the width of the image is adjusted to the display area and the portion of the image is displayed as shown in FIG. 2, or the height of the image is reduced by adjusting to the display area and the image is displayed as shown in FIG. 3.
Additionally, with the conventional method for displaying a document image, if an entire document image is reduced and displayed, or if part of the document image is displayed, the document is displayed as the layout of the original document sets out. That is, even if the reducton ratio of the document image shown in FIG. 1 is different as shown in FIGS. 2 and 3, the document image is displayed according to the same layout of the original document.
Therefore, the conventional method for displaying a document image has the problem that characters become small and are difficult to read if the image is reduced in order to display the entire image, while the area for displaying the characters becomes smaller if the characters are displayed larger for ease of reading.
As the difference between the numbers of pixels of a document image and a display device becomes larger, or as the physical display area of the display device is smaller, the problem becomes bigger. Especially, this problem becomes more serious when the document image is displayed by a portable information device.
An object of the present invention is to provide a document image display method and a display device for displaying more of a desired portion of a document image whose number of pixels is large, and which is scanned at high resolution, on a display device whose number of pixels is smaller than that of the document image for ease of viewing.
The document image display method according to the present invention comprises: a partial image extracting step for structurizing a document image as a display target by dividing the image into areas according to attributes, and extracting the respective structurized areas as partial images; and an image storing step for storing the partial images extracted from one document in the above described partial image extracting step as one file.
The document image display method according to the present invention further comprises, for example, a data reading step for selecting and reading the partial images stored as one file in the above described partial image extracting step; and an image displaying step for independently displaying each partial image read in the data reading step.
Additionally, for example, a priority is assigned to the partial image in one document according to the attribute of the extracted partial image in the above described partial image extracting step; and the data of the priority assigned to the partial image together with the partial image are stored in the above described image storing step.
Furthermore, for example, the data of each partial image is reduced at a plurality of stages and stored.
With the document image display method according to the present invention, one document image is divided into a plurality of partial images, and each of the plurality of partial images is manipulated, so that the partial images can be displayed in various forms according to a user desire. For example, the partial images can be displayed in descending order of priorities assigned to the respective partial images; the partial image that a user desires to view can be first displayed by displaying an image reduced at a stage according to a priority; or an image reduced at a stage, which is easy to view, can be displayed.